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Moisture Assessment

Moisture Assessment. WEATHERIZATION ENERGY AUDITOR SINGLE FAMILY. WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012. Learning Objectives. Moisture Assessment. By attending this session, participants will be able to:

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Moisture Assessment

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  1. Moisture Assessment WEATHERIZATION ENERGY AUDITOR SINGLE FAMILY WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012

  2. Learning Objectives Moisture Assessment By attending this session, participants will be able to: • Analyze the symptoms of moisture problems in houses. • Identify moisture sources. • Explain moisture terms and concepts. • Demonstrate how to measure relative humidity. • Demonstrate how to use a psychrometric chart. • Apply moisture control strategies. • Use moisture assessment tools.

  3. Symptoms #1 Moisture Assessment Excessive window condensation Photo courtesy of PA WTC

  4. Symptoms #2 Moisture Assessment Frost on underside of roof sheathing Photo courtesy of PA WTC

  5. Symptoms #3 Moisture Assessment Mold on interior surfaces Photo source: PA WTC Photo Photo courtesy of PA WTC

  6. Symptoms #4 Moisture Assessment Peeling Exterior Paint Photo courtesy of PA WTC

  7. Symptom #5 Moisture Assessment Standing Water in Basements Photo courtesy of PA WTC

  8. Moisture Sources Moisture Assessment • Foundations • Unvented space heaters • Unvented dryers • Disconnected ventilation fans • Drying wood indoors • Excessive mechanical or passive humidification Photo courtesy of PA WTC These water stains are a result of fan venting into the attic.

  9. Sources of Water Vapor Moisture Assessment

  10. Important Terms and Concepts Moisture Assessment • Condensation: water vapor transformed to liquid water • Evaporation: liquid water transformed to water vapor • Absolute humidity (vapor pressure): the ratio of water vapor to a given volume of air • Relative humidity (RH): the ratio of the amount of moisture in the air compared to amount of moisture that the air can hold • Dew point: the temperature at which condensation occurs

  11. Measuring Relative Humidity Moisture Assessment • Sling Psychrometers • Two thermometers side by side • One is wrapped in wet wick (wet bulb), the other is dry (dry bulb) • Spinning it around speeds temperature stabilization • Plot wet bulb and dry bulb temperature on psychrometric chart to determine dew point and RH Photos courtesy of Bacharach

  12. Psychrometric Chart #1 Moisture Assessment Dry bulb = 80° Wet bulb = 66° Dew point = 60° RH = 50% Grains of water per pound of dry air

  13. Psychrometric Chart #2 Moisture Assessment 156 78 Grains of water per pound of dry air

  14. Psychrometric Chart #3 Moisture Assessment Grains of water per pound of dry air

  15. Psychrometric Chart #4 Moisture Assessment Grains of water per pound of dry air

  16. Psychrometric Chart #5 Moisture Assessment Grains of water per pound of dry air

  17. RH: Things to Remember Moisture Assessment • Warm, wet air contacting cold surfaces creates condensation instantly. • Cold winter air typically contains very little moisture and therefore has a low RH. When that air is heated, the RH drops even lower. • RH below 15% can lead to respiratory problems, failure of furniture glue and other problems.

  18. Floored Attic and First Condensing Surface Attic Case Study Moisture Assessment Photo courtesy of PA WTC

  19. Attic Case – Causes & Solutions Moisture Assessment Possible Causes • Moderate to high interior moisture source • Attic surface temps are below the dew point of the indoor air • Air leaks to attic Control Strategies • Source control • Air seal the attic

  20. Basement Case Study Moisture Assessment • Symptom • Condensation evident on basement walls • Reason • Light to moderate interior moisture source • Basement walls are below the dew point of the indoor air Mold on cool interior corner Photo courtesy of PA WTC

  21. Basement Case Study Solutions Moisture Assessment Control moisture sources. Remove susceptible materials. Educate occupants to: • Mechanically dehumidify. • Increase air flow in basement (fans). • Close basement openings during hot humid periods.

  22. Crawl Space Case Study Moisture Assessment Symptoms • Wet wood • Condensation on foundation surfaces Possible Reasons • High ground moisture source • Warm humid air entering vents from outside • Crawl space surfaces are below the dew point of the outside air Photo courtesy of PA WTC Water droplets of condensation on AC ducts.

  23. Crawl Space Case Study Solutions Moisture Assessment • Install a ground vapor retarder. • Control moisture sources and remove susceptible materials. • Consider converting to a conditioned crawl space. Photo courtesy of INCAP Conditioned crawlspace with air sealed and insulated walls.

  24. Tools of the Trade Moisture Assessment Clear understanding of moisture management principles. • Senses - Visual inspection • Evidence of condensation • Evidence of mold • Communication Skills • Know what questions to ask • Documentation is vital • Wood Moisture Meter • To make quantitative assessments on wood moisture content • Psychrometer • To determine real time RH levels • Digital Camera

  25. Moisture Meters Moisture Assessment Photos courtesy of PA WTC PhotoSource: PA WTC

  26. Summary Moisture Assessment • The first step in doing a moisture assessment is to look for visible signs of moisture and moisture sources in the house. • Plotting the wet bulb and dry bulb temperatures on a psychrometric chart gives dew point and relative humidity. • Understanding the effects of temperature and vapor pressure on RH can help identify solutions. • Source control, air sealing, ventilation, and thermal improvements are important moisture mitigation strategies. • Photos and diagnostic equipment help document existing conditions.

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